A frequency converter that performs dual frequency conversion is provided. The frequency converter restricts noise occurrence and enables signal transfer with good linearity. The frequency converter performs dual conversion of a first signal (RF(+) and RF(-)) by using two signals including a second signal (LO1 (+) and LO1 (-)) and a third signal (LO2 (+) and LO2 (-)). Using a balun and an amplifying circuit that performs input/output operations in a single-ended manner, the frequency converter restricts NF degradation. By feeding optimum values of current into the first and second switching circuits and into the amplifying circuit, NF and linearity are optimized. The balun, the amplifying circuit, and the first and second switching circuits are formed on the same semiconductor substrate.